Business
Jobs
  • About Us
  • Solutions
    • Job Postings
      Post your job and receive qualified candidates in 48h.
    • Candidate Assessments
      500+ technical and psychological tests, plus anti-fraud.
    • Headhunting
      Tailor-made executive search from start to finish.
    • Payroll + EOR
      Payroll dispersal and EOR across 15+ LATAM countries.
  • Pricing
  • Jobs

0

271
Views
How do I decrease and increase height of div on scroll with JavaScript only?

JavaScript

var changeHeight = () => {
    let flag = 0;
    while(flag != 1) {
        size += 1;
        return size;
    }
    if(size == window.innerHeight/2){
        flag == 1;
    }
    
}
var size = 5;
document.body.style.height = "10000px";
const div = document.createElement("div");

div.style.width = "100%";
div.style.position = "fixed";
div.style.left = "0";
div.style.top = "0";
div.style.backgroundColor = "green";
document.body.appendChild(div);

window.addEventListener("scroll", changeHeight);
div.style.height = size + "px";

HTML

It's empty with only <script src="script1.js"> </script> inside

What do I want to achieve?

I want to create stick to the top of the page object while scrolling which increases height until height == window.innerHeight/2 after this, scrolling should decrease it's size.

My problem is that I cannot return size variable over the function, or is there something more wrong?

about 4 years ago · Juan Pablo Isaza
2 answers
Answer question

0

while is unnecesery in this case and you don't have any code that will tell this element to decrease its size.

In this example given element will decrease and increase its size back and forth

let size = 5;
let flag = 0;

const step = 1;

const changeHeight = () => {
    if(size >= window.innerHeight / 2 && flag === 0){
        flag = 1;
    } else if (size <= 0 && flag === 1) {
        flag = 0;
    }

    div.style.height = `${flag ? size-=step : size+=step}px`;
}

document.body.style.height = "10000px";
const div = document.createElement("div");

div.style.width = "100%";
div.style.position = "fixed";
div.style.left = "0";
div.style.top = "0";
div.style.backgroundColor = "green";
document.body.appendChild(div);

window.addEventListener("scroll", changeHeight);
<html>
  <body>
  </body>
</html>

about 4 years ago · Juan Pablo Isaza Report

0

var size = 5;
var halfWay = false;

const changeHeight = () => {

    console.log("size", size);
    if (size <= window.innerHeight / 2 && !halfWay) halfWay = false;
    else halfWay = true;

    if (!halfWay) {
        // If the height is less than or equal to the windows inner height increase the height of the div element.
        size += 1;
        return size;
    }
    else if (halfWay && size > 5) {
        // If the height has come down to the halfway point of the windows inner height then decrease the height of the div element.
        size -= 1;
        return size;
    }
    else {
        // Resets to original values
        halfWay = false;
        size = 5;
        return size;
    }

    // Original code.
    /*       let flag = 0;
           console.log("b4", size);
           while (flag != 1) {
               size += 1;
               console.log("after", size);
               return size;
           }
           if (size == window.innerHeight / 2) {
               flag = 1;
           }
           */
}

document.body.style.height = "10000px";
const div = document.createElement("div");

div.style.width = "100%";
div.style.position = "fixed";
div.style.left = "0";
div.style.top = "0";
div.style.backgroundColor = "green";
div.style.height = "5px";
document.body.appendChild(div);

console.log("Window innerHeight:", window.innerHeight);

window.addEventListener("scroll", () => {
    div.style.height = changeHeight() + "px";
    console.log("size in listner:", size);
});
about 4 years ago · Juan Pablo Isaza Report
Answer question
Find remote jobs

Discover the new way to find a job!

Top jobs
Top job categories
Business
Post vacancy Pricing Sales
Legal
Terms and conditions Privacy policy
© 2026 PeakU Inc. All Rights Reserved.
Andres GPT
Show me some job opportunities
There's an error!